Controversial plans for a ‘snoopers’ charter’ were in turmoil last night after 40 Tory MPs threatened a full-scale revolt.

They are demanding major changes to the Communications Bill, which currently would allow the monitoring of the public’s every phone call, email and internet click.

The backbenchers also say the Bill’s scope must be limited to terrorism and the ‘most serious crimes’ if Britain is not to be turned into a nation of suspects.

Controversial: The Communications Bill would force providers to keep databases of phone and computer activity for a year. Forty Tory MPs have threatened a full scale revolt

A further concern, they argue, is that the 2billion projected cost is not ‘robust’ and could spiral.

Deputy Prime Minister Nick Clegg has already demanded the Government return to the ‘drawing board’. Now Tory MP Dominic Raab has collected the names of 40 colleagues who will sign an open letter opposing the Bill unless it is substantially amended.

The prospect of a rebellion by both Coalition parties means ministers may have to rely on Labour support. However, the Opposition has yet to say where it stands on the contentious issue.

Deputy Prime Minister Nick Clegg has already demanded the Government return to the drawing board

The law would force communications providers to keep databases of phones and computer activity for a year. Data would be accessed by a computer ‘filter’ used by police or security officials. The MPs are alarmed by the risk of the filter being misused.

David Cameron has insisted his Government is committed to the Bill, but a revolt by his MPs may be a lethal blow to its passage.

Last night, Mr Raab said: ‘It’s one thing to target terrorists and serious criminals, another to turn us into a nation of suspects. This looks like the mother of all Whitehall IT projects. It needs to be tailored to focused law enforcement if it is going to pass muster.’

The letter, written by Mr Raab, says: ‘There has been no proper explanation of how [clauses in the Bill] concerning “filtering arrangements” will work in practice.

‘It is clear that they would authorise … techniques designed to infer potentially suspicious activity from the patterns of mass data held on every innocent citizen in this country.’

Mr Raab said the 40 MPs include 19 first elected in 2010, a group who have proved they will take a stand on issues of importance. These 40 number more than all 38 backbench Lib Dems.

Tory MP Nick de Bois warned the Bill could lead to more intrusive measures. He said: ‘What we decide here could be modified by future governments. Much more protection needs to be written in.’

A Home Office spokesman said: ‘Two committees who examined the Bill recognised the need for new laws. There is a pressing need to update the legislation.’